so it is still possible to run out of the resources

Yes, but I would rather see this as a sign that you hit a wall with your motivation-creating skill, than a limitation on how much motivation you can have or how quickly you can achieve it. There seems to be plenty of evidence for people having success spirals that are very quick and powerful.

Also, the correct meta-strategy when you have little motivation seems to be to direct as much of it as you can towards exploring ways to get more motivation. I expect most people are not strategic about their motivation, so I point it out whenever I can.